Question on G25

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Lucy Dong 1G
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Question on G25

Postby Lucy Dong 1G » Sun Sep 25, 2016 9:10 pm

Practitioners of the branch of alternative medicine known as homeopathy claim that very dilute solutions of substances can have an effect. Is the claim plausible? To explore this question, suppose that you prepare a solution of a supposedly active substance, X, with a molarity of 0.10 mol x L(-1). Then you dilute 10. mL of that solution by doubling the volume, doubling it again, and so on, for 90 doublings in all. How many molecules of X will be present in 10. mL of the final solution?

The answer in the solutions manual confused me, so I was wondering if there is an easier way to approach this. Thanks!

Chem_Mod
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Re: Question on G25

Postby Chem_Mod » Mon Sep 26, 2016 9:52 pm

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Angela_Kim_1N
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Re: Question on G25

Postby Angela_Kim_1N » Mon Sep 26, 2016 11:13 pm

For the solution above, is 0.050M necessary to figure out the answer to this problem?

Chem_Mod
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Re: Question on G25

Postby Chem_Mod » Tue Sep 27, 2016 12:42 am

No, it is not required. The calculation for the 0.050M is to show how to do the calculation for the first dilution.

Ning_Yao_1B
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Re: Question on G25

Postby Ning_Yao_1B » Wed Sep 28, 2016 10:23 pm

I have a basic question for G25.
If diluting a solution does not change the moles/ molecules of solute in the solution, then why does the amount of X in this question will decrease?
Doesn't the moles/ number of molecules of X have to stay the same?

Vivian Wang 3J
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Re: Question on G25

Postby Vivian Wang 3J » Thu Sep 29, 2016 3:37 pm

Moles of solute stays the same for diluting and molarity changes.
However, when you take a smaller volume of a solution, molarity stays the same, but moles of solute will decrease.


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